Active Humidity Control Through Gas-Fired Desiccant Humidity Pump

Abstract

High equipment first cost and high operating costs, if electricity is used to drive such a system, have prohibited the application of active humidity control equipment in comfort conditioning in the past. Instead, passive techniques have been applied. A comparison of passive capacity control methods to control humidity shows that only the combined face and bypass and variable air volume system shows improved performance with respect to space humidity control, dew point depression, and response to perturbations. A gas-fired desiccant humidity pump will provide economical humidity control in existing and new construction using VAV or constant volume air distribution systems. The humidity pump is designed as a packaged make-up air module. It is coupled to new or existing conventional air-conditioning system via a duct. It consists of a triple integrated heat-exchanger combining (liquid) desiccant dehumidification with indirect evaporative cooling, a brine interchanger, and a gas-fired brine heater to regenerate the desiccant. Field experiments of two humidity pumps on existing commercial buildings have been initiated. Each system dehumidifies 5000 scfm of make-up air to meet all the latent loads, which is then fed to conventional, electric-driven HVAC equipment which meet all the sensible loads.